1. Technical Field
The present invention relates to a method and an apparatus for measuring an ion beam inclination of an ion implantation apparatus for manufacturing a semiconductor device, and more particularly to a method and an apparatus for measuring an inclination angle of an ion beam by using ions implanted into an ion current.
2. Description
Generally, a semiconductor device is manufactured by repeatedly performing various unit processes, such as deposition, photolithography, etching, ion implantation, polishing, cleaning and drying processes. When the ion implantation process is carried out, an ion beam including predetermined ions collides with a predetermined region of a semiconductor wafer, thereby implanting ions into the predetermined region of the semiconductor wafer. As compared with a thermal diffusing technique, the ion implantation process has an advantage that the number of ions implanted into a predetermined region and the implantation depth can be adjusted. Examples of ion implantation apparatuses and ion implantation systems are disclosed in U.S. Pat. No. 5,343.047 (issued to Ono, et. al) and U.S. Pat. No. 5,641,969 (issued to Cooke, et. al).
The amount of ions implanted into the ion current is adjusted based on the ion current measured by a Faraday cup assembly. In addition, in order to avoid the channeling effect that ions implanted into the ion current pass through an empty space, the ion current is required to have a predetermined inclination angle. That is, when the ion beam is horizontally incident into the ion current, the ion current has an inclination angle of 7° with respect to a vertical plane. However, even when a central axis of an ion source is in parallel with a horizontal plane, it cannot be measured whether or not the advancing direction of the ion beam is in parallel with the horizontal plane. If the advancing direction of the ion beam is not in parallel with the horizontal plane, the channeling effect or a shadow effect created by a mask formed on the ion current is generated.
In addition, if the advancing direction of the ion beam is not in parallel with the horizontal plane, the Faraday cup assembly cannot precisely measure the ion current, because the amount of the ions accommodated in the horizontally positioned Faraday cup assembly varies depending on the inclination angle of the ion beam with respect to the horizontal plane. For this reason, the real amount of ions implanted into the ion current is different from an intended amount of ions, thereby causing process failures such as an overdose or an underdose.
It is a first object of the present invention to provide a method for measuring an inclination angle of an ion beam incident into a predetermined region of an ion current and a method for implanting ions into the predetermined region of the ion current.
A second object of the present invention is to provide an apparatus for measuring an inclination angle of an ion beam incident into a predetermined region of an ion current and an apparatus for implanting ions into the predetermined region of the ion current.
In one aspect, the present invention provides a method for measuring an inclination angle of an ion beam. In the above method, the ion beam supplied from an ion source is received and a variation of an ion current of the ion beam is measured while varying an angle of the ion beam to be received. The inclination angle of the ion beam is calculated based on the variation of the ion current.
According to another aspect of the present invention, there is provided a method for measuring an inclination angle of an ion beam. A Faraday cup assembly is installed in an advancing path of the ion beam supplied from an ion source, to receive the ion beam. A first variation of the ion current caused by the ion beam received in the Faraday cup assembly is measured by rotating the Faraday cup assembly about a horizontal axis, which is vertically crossed with a vertical plane including a central axis of the ion source and passes through the Faraday cup assembly. A first maximum value of the ion current from the first variation is detected and a first inclination angle of the ion beam is calculated based on a first rotation angle, which is corresponding to the first maximum value, of the Faraday cup assembly rotated about the horizontal axis. A second variation of the ion current is measured by rotating the Faraday cup assembly about a vertical axis, which passes through a cross point of the central axis of the ion source and the horizontal axis and a second maximum value of the ion current the second variation is detected and a second inclination angle of the ion beam is calculated based a second rotation angle, which corresponds to the second maximum value, of the Faraday cup assembly rotated about the vertical axis.
According to still another aspect of the present invention, there is provided a method for implanting ions. In the method, an ion beam supplied from an ion source is received and a variation of an ion current of the ion beam is measured while varying an angle of the ion beam to be received. An inclination angle of the ion beam is calculated based on an angle of the ion beam to be received and the variation of the ion current. After placing a wafer having a critical angle, corrected according to the inclination angle of the ion beam, in an advancing path of the ion beam, ions of the ion beam are implanted into an entire surface of the wafer while moving the wafer.
In a further aspect, the present invention provides an apparatus for measuring an inclination angle of an ion beam. The apparatus includes a first means for receiving the ion beam supplied from an ion source, and for measuring an ion current of the received ion beam; a second means for varying an align angle of the first means to adjust an amount of the ion beam received in the first means; and a third means for calculating the inclination angle of the ion beam based on the align angle of the first means and the variation of the ion current caused by the variation of the align angle of the first means.
According to a still further aspect of the present invention, there is provided an apparatus for measuring an inclination angle of an ion beam. The apparatus includes: a Faraday cup assembly installed in an advancing path of the ion beam supplied from an ion source, to receive the ion beam; a current/voltage converting means for converting an ion current generated from the Faraday cup assembly due to the ion beam, into an ion voltage; a voltage measuring section for measuring the ion voltage; a driving means for rotating the Faraday cup assembly about a horizontal axis, which is vertically crossed with a vertical plane including the central axis of the ion source and passes through the Faraday cup assembly, to vary a first align angle of the Faraday cup assembly and for rotating the Faraday cup assembly about a vertical axis, which passes through a cross point of the central axis of the ion source and the horizontal axis, to vary a second align angle of the Faraday cup assembly; an angle measuring means for measuring a first rotation angle of the Faraday cup assembly rotated about the horizontal axis and a second rotation angle of the Faraday cup assembly rotated about the vertical axis; a data analyzing section connected to the voltage measuring section for detecting first and second maximum values of ion current measuring data by analyzing first and second variations of the ion current measuring data corresponding to the first and second align angles of the Faraday cup assembly and for calculating the inclination angle of the ion beam based on the first and second rotation angles corresponding to the first and second maximum values; and an angle adjusting section for generating a control signal to adjust the first and second align angles of the Faraday cup assembly.
According to yet a further aspect of the present invention, to accomplish the second object, there is provided an ion implantation apparatus. The ion implantation apparatus includes: an ion implantation chamber for performing an ion implantation process with respect to a wafer and including a chuck for gripping the wafer; an ion source connected to the ion implantation chamber for supplying an ion beam including ions into the ion implantation chamber; an ion current measuring means installed in an advancing path of the ion beam when measuring an inclination angle of the ion beam for receiving the ion beam and for measuring an ion current of the ion beam received therein; an angle varying means for varying an align angle of the ion current measuring means so as to adjust an amount of the ion beam received in the ion current measuring means; an inclination angle calculating means for calculating the inclination angle of the ion beam based on the align angle of the ion current measuring means and a variation of the ion current caused by a variation of the align angle of the ion current measuring means; a first driving means for driving the ion current measuring means up and down; and a second driving means for placing the wafer in the advancing path of the ion beam while ions are being implanted into the wafer, rotating the wafer with a critical angle corrected according to the inclination angle of the ion beam, and moving the wafer for allowing ions to be implanted into a whole area of the wafer.
By measuring the inclination angle of the ion beam, the incident angle of the ion beam, which is incident into the wafer during the ion implantation process, can be precisely adjusted to a predetermined critical angle. Accordingly, the channeling effect and shadow effect can be effectively prevented. The amount of the ions included in the ion beam can be precisely measured, so the amount of ions implanted into the wafer can be precisely adjusted.